The use of sizepress solutions for finishing paper and textiles is well known. For instance, it is known to apply pigmented sizepress solutions to paper in the 10% solids range. However, with the use of foam, it is possible to apply the same solution at higher solids (ca. 20%). By applying a higher solids solution, less energy is required to dry the web resulting in reduced energy costs and increased machine speed. In addition, decreasing the sizepress density by air entrainment permits greater flexibility in controlling pickup by the paper.
U.S. Pat. No. 3,210,240 teaches the use of a foamed starch material for sizing paper to improve the bonding between the top surface fibers and the bodies of such papers for enhanced strength and water penetration resistance. U.S. Pat. Nos. 4,208,485 and 4,266,976 teach the use of foamed fabric treating compositions for treating the fabrics to increase fiber strength, flame retardance and resistance to abrasion. In each of these cases, the use of foaming agents is desirable because the foamed compositions require less water or solvent than other types of applications.
The key to a good foaming agent, particularly where the foamed composition is applied to paper substrates, depends upon its ability to reduce the density of the foamed composition to the lowest possible value at a given solids and with a minimum concentration of foaming agent. The prior art mentioned hereinbefore suggests several foaming agents, and combination of foaming agents that have been found to be acceptable for making foam compositions. However, none of the prior art foaming agents achieve the same level of effectiveness produced by the combination of ingredients disclosed herein.